Unless it’s a 15+ letter word that ends in U, this one won’t work
I was trying to highlight where the letters we already had were. I was trying to conceptualize various ideas about vulnerabilities in foursquares and then realized none of that matters if you can’t find a good keyword. The problem is in how you fill the table after your keyword. The U in that position means that you cannot correctly fill your foursquare encryption/decryption charts.
Kryptos - Beyond K4 